Add hotkey combinations in pad-2-keyboard

Add all possible Hotkey combinaison in p2k, except:

• Hotkey + (hotkey or select) : does not make sense
• Hotkey + start : reserved

Syntax:

• 0:a = f1 ;; Press F1 using button A
• 0:+a = f2 ;; Press F2 using Hotkey + button A